A Triple Axial Chirality, Racemic Molecular Semiconductor Based on Thiahelicene and Ethylenedioxythiophene for Perovskite Solar Cells: Microscopic Insights on Performance Enhancement

摘要

For the low-cost fabrication of large-area, durable perovskite solar cells, it is of pivotal importance to engineer organic semiconducting films with a combined property of matched energy level, sufficiently large conductivity, high glass transition temperature, and excellent solution processability. Toward this goal, herein an in silico tailored molecular semiconductor (T5HE-OMeTPA) with triple axial chirality, by joint use of thia[5]helicene and ethylenedioxythiophene, is reported. T5HE-OMeTPA with a reduced reorganization energy of hole transfer can be exploited as the hole transport layer for perovskite solar cells with 21% efficiency, which also display excellent long-term stability at 60( )degrees C. The doped, sufficiently conductive T5HE-OMeTPA composite with a glass transition temperature of 121 degrees C not only exhibits persistent film morphology under thermal stress, but also surprisingly damps the motion of diffusive components of perovskite for a better control of the degradation of photoactive layer. The translational motion of both ions and molecules is intrinsically associated with the glass transition of a doped molecular semiconductor composite, which is in stark contrast to the microscopic fashion for the glass transition of an undoped molecular semiconductor, that is, thermally activated rotation of diphenylamine.